The aim of the experiments will be purification of the dominant protein species constituting particles characteristic of the lumenal plasma membrane of the sheep urinary bladder. Once isolated in sufficient quantity, this particle will be analyzed to determine its composition and subunit structure. The isolates will then be used as anitgens to produce specific antibodies. The latter in turn will be used for immunocytochemical identification and localization of the specific protein within the isolated lumenal membranes and within intact urothelial cells. These experiments will test the hypothesis that the isolated protein corresponds to the particle constituting hexagonal membrane. Reconstitution of plaques from isolated particles and lipids will be attempted. These experiments are designed to further define this membrane, which is tentatively identified as one resistant to water transport, and to obtain a basis for its comparison with membranes made hyperplastic by exposure to carcinogens.